[The sandwich enzyme-linked immunoabsorbent assay of serum transferrin receptor by using monoclonal and polyclonal antibodies]

The human placenta transferrin receptor was purified in the form of transferrin-transferrin receptor complex (Tf-TfR), and a monospecific polyclonal antibody against TfR was developed by a Tf-coupled Sepharose 4B affinity chromatography to remove the anti-Tf components in the antiserum. A sandwich enzyme-linked immunoabsorbent assay (ELISA) was established for measuring serum transferrin receptor (sTfR) by using monoclonal antibody OKT9 and monospecific polyclonal antibody. This method is simple, specific and sensitive and has a good accuracy. The measurement of sTfR showed that the level of normal children was 4.54 +/- 1.08 mg/L. There were increased levels of sTfR in patients with severe iron deficiency anemia and those with hemolytic anemia (13.92 +/- 4.45 mg/L and 9.94 +/- 3.22 mg/L, respectively). In patients with aplastic anemia, the level was decreased (2.06 +/- 0.82 mg/L). These results indicate that the sTfR measurement has a differential significance for diagnoses of various anemia.

Requirement of the self-glucosylating initiator proteins Glg1p and Glg2p for glycogen accumulation in Saccharomyces cerevisiae

Glycogen, a branched polymer of glucose, is a storage molecule whose accumulation is under rigorous nutritional control in many cells. We report the identification of two Saccharomyces cerevisiae genes, GLG1 and GLG2, whose products are implicated in the biogenesis of glycogen. These genes encode self-glucosylating proteins that in vitro can act as primers for the elongation reaction catalyzed by glycogen synthase. Over a region of 258 residues, the Glg proteins have 55% sequence identify to each other and approximately 33% identity to glycogenin, a mammalian protein postulated to have a role in the initiation of glycogen biosynthesis. Yeast cells defective in either GLG1 or GLG2 are similar to the wild type in their ability to accumulate glycogen. Disruption of both genes results in the inability of the cells to synthesize glycogen despite normal levels of glycogen synthase. These results suggest that a self-glucosylating protein is required for glycogen biosynthesis in a eukaryotic cell. The activation state of glycogen synthase in glg1 glg2 cells is suppressed, suggesting that the Glg proteins may additionally influence the phosphorylation state of glycogen synthase.

[Association of plasma insulin with blood pressure and sodium sensitivity in children]

To study the relationship between plasma insulin level, sodium sensitivity and blood pressure, 150 children aged from 10 to 15 years with high blood pressure and 150 children matched for age and sex but with normal blood pressure were measured for plasma insulin with radioimmunoassay and sodium sensitivity with the tests of oral saline load and furosemide sodium-volume depletion and followed for 5 years. The results showed that (1) In children with HBP and positive family history of hypertension (FH+), the plasma insulin level was significantly higher than that in the respective control group (P < 0.01); (2) In children with high plasma insulin level, the percentiles of systolic blood pressure kept high and had a rising tendency during the follow-up period; (3) In children with sodium sensitivity, the plasma insulin level was higher than that in children with sodium resistance (P < 0.01) and the plasma insulin level correlated positively with blood pressure increasing rate of post-load (P < 0.05). It is suggested that insulin resistance was associated with sodium sensitivity, and they might play a role in the development of hypertension in childhood.

Administration of recombinant interleukin 12 prevents outgrowth of tumor cells metastasizing spontaneously to lung and lymph nodes

The present study investigates the ability of recombinant interleukin 12 (rIL-12) to modulate the growth of a primary tumor as well as the outgrowth of metastatic tumor cells in an ovarian carcinoma (OV-HM) model. This aggressive tumor displayed rapid growth of the primary tumor mass, high incidence of metastases to lung and lymph nodes, and invasion from the primary s.c. site to the peritoneal cavity. Starting 12 days after s.c. tumor cell implantation, several i.p. injections of rIL-12 at 2-3 day intervals resulted in regression of growing tumors. These treated mice did not show signs of metastases or tumor recurrence at the original site. One month after tumor implantation, untreated mice did not have visible lung metastasis, but some did have palpable lymph nodes. At this stage, the primary tumors of animals without palpable lymph nodes were surgically resected. When examined 2 months later, most animals had developed lymph node and lung metastases. In contrast, rIL-12 injections after tumor resection inhibited the development of metastases in both lung and lymph nodes. This contrasted with the failure of IL-2 to prevent metastases. Even for mice already showing signs of lymph node metastases or invasion of the abdominal wall, rIL-12 administration after tumor resection prevented further invasion to the peritoneal cavity and growth of metastatic tumor cells in lung. It was somewhat surprising that the IL-12 treatment of animals after 1 month of tumor growth without resection also resulted in complete tumor regression, as well as eradication of micrometastasis that would have occurred before the treatment. Moreover, they exhibited resistance to a rechallenge with the same tumor but not with a second tumor. Thus, this tumor system provides a relevant model to clinical situations in terms of treatment of advanced tumors and metastases. These results also indicate that IL-12 can induce a curative immune response, even in the face of an aggressive micrometastasizing tumor.

[Isolation and identification of extrem thermophilic bacteria from hot springs of Sichuan and Tibet]

Eleven strains of extrem thermophilic bacteria belonging to the Bacillus Stearothermophiles were isolated from the hot springs of Sichuan and Tibet. The cells were gram-positive, sporulating and motile. The optimum temperature for growth was between 65 degrees C to 70 degrees C; the maximum 94 degrees C, and minimum 40 degrees C. The colour of colony was yellow to bright orange. The G+C content of the DNA in strains has been found to be in the range 48.4-53.15 mol%.

[Production and characterization of monoclonal antibody against aflatoxin B1]

Two hybridoma cell lines 1B5 and 2F1 capable of secreting specific monoclonal antibodies (McAbs) against aflatoxin B1 (AFT B1) were obtained. BALB/c mice were immunized by intrasplenic injection of AFT B1-human serum albumin conjugate (AFT B1-HSA) containing 9 AFT B1 residue per molecule. Spleen cells of BALB/c mouse with high serum antibody titer were fused with SP 2/0 myeloma cells in the presence of polyethylene glycol. Hybridoma cell lines were selected by using an indirect ELISA with AFT B1-keyhole limpet haemocyanin as coating antigen and grown as ascite tumour cells in BALB/c mice which previously had received an intraperitoneal injection with Freund's incomplete adjuvant. The McAbs were found to have strong reaction with AFT B1-bovine serum albumin conjugate (AFT B1-BSA) and no reaction with HSA or BSA. The reactivity of the McAbs with AFT analogs was determined by an indirect inhibition ELISA and the concentrations (ng/ml) required to inhibit 50 binding of McAb to AFT B1-BSA conjugate solid phase were AFT B1 4.0ng/ml, B2 36.9ng/ml, G1 23.3ng/ml and G2 403.3ng/ml for 1B5 McAb, and AFT B1 2.4ng/ml, B2 2.6ng/ml, G1 2.8ng/ml and G2 4.7ng/ml for 2F1 McAb.

Role of cyclic AMP dependent protein kinase in cannabinoid receptor modulation of potassium "A-current" in cultured rat hippocampal neurons

Cannabinoid receptor agonists have been previously shown to enhance a potassium A-current (IA) in cultured rat hippocampal neurons. This effect has been further demonstrated to be dependent on G-protein linkage to adenylyl cyclase and levels of intracellular cyclic AMP (cAMP). The present study extends this analysis to the involvement of cAMP-dependent protein kinase (PKA) in this cascade. Specific activators and inhibitors of PKA were shown to have differential effects on the voltage dependence of IA. Specific activators of PKA produced a negative shift in voltage dependence of IA, whereas PKA inhibitors produced a positive shift in IA voltage dependence, the latter similar to that effected by the cannabinoid agonist WIN 55,212-2. Although the negative shift in IA induced by PKA stimulation could be reversed by PKA inhibitors, the positive shift produced by the PKA inhibitors alone was only 50-60% of the cannabinoid-produced shift in IA voltage dependence. This partial effect of PKA inhibition was confirmed by biochemical assays in the same cultured neurons that showed a similar 50-60% decrement in in vitro protein phosphorylation produced by PKA inhibitors. Results are discussed in terms of a diffusible second messenger linkage of the cannabinoid receptor to the A-current channel via the role of protein phosphorylation in modulation of IA.

Cannabinoids modulate voltage sensitive potassium A-current in hippocampal neurons via a cAMP-dependent process

Previous studies have shown that cannabinoid receptor analogs increase voltage-dependent potassium A-current (IA) in cultured hippocampal cells. Because cannabinoid receptors inhibit adenylate cyclase, the present study explored whether cAMP played a role in mediating this effect on IA. The specific issue of whether cannabinoid receptor modulation of voltage-dependent IA acts via a cAMP-dependent process was investigated. The cAMP analog, 8-bromo-cAMP, as well as the adenylate cyclase stimulant forskolin, produced concentration-dependent shifts in IA that were opposite those produced by cannabinoid receptor ligands. Moreover, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine also produced a marked negative shift in the steady-state voltage dependence of IA and increased the effect of forskolin on IA. As shown in previous studies, the cannabinoid agonist WIN 55,212-2 increased IA via a decrease in steady-state voltage-dependent inactivation of IA. WIN 55,212-2 also reversed the effects of forskolin on IA. The electrophysiological studies were paralleled by direct assays of cAMP in these cells, where cannabinoids inhibited forskolin-stimulated cAMP by 50% in a pertussis toxin-sensitive manner. The results confirmed that pertussis toxin-sensitive cannabinoid receptor-mediated changes in IA were probably the result of inhibition of adenylate cyclase. The findings are discussed in terms of modulation of IA conductance properties via cannabinoid receptor-mediated inhibition of cAMP levels within the cell.

[Production and identification of monoclonal anti-idiotype antibodies against anti-phenolic glycolipid-I antibody of Mycobacterium leprae]

Hybridoma (4C4) secreting monoclone anti-idiotype antibody (McAb2) against anti-phenolic glycolipid-I (PGL-I) antibody (Ab1) was produced by fusion of SP2/0 myeloma cells and spleen cells of syngeneic mice which had been previously tolerant to human IgM 4C4 monoclone anti-idiotype antibody was identified with a series of experiments including competitive and neutralizing inhibition ELISA. It was found that the binding of McAb2 with rabbit anti-PGL-I antibody could be competitively inhibited by NT-O-BSA (synthetic analog of PGL-I) and neutralized by polyclonal anti-PGL-I antibody derived from various origins (human or rabbit); McAb2 could block the binding of purified human Ab1 with NT-O-BSA. The assay of McAb2 as mimic antigen demonstrated that McAb2 could substitute for NT-O-BSA in leprosy serodiagnosis. These results show that anti-idiotype antibody produced by 4C4 is a monoclone anti-idiotype antibody bearing internal image of PGL-I and possibly can be used in leprosy serodiagnosis.

[Study on the induction of active immunity in human by injecting human anti-HBs antibodies]

One hundred and three health volunteers were injected with various doses of human anti-HBs (Ab1). The anti-idotypic antibodies (Ab2) and anti-antiidiotypic antibodies (Ab)3 in sera were tested at intervals of 30 days with ELISA. We found that the dynamic changes between Ab2 and Ab3 of immune sera were cyclical by way of their interaction and the Ag-specific Ab3 were the same as Ab1 in specificity. The results reconfirmed that exogenous human anti-HBs could induce active immunity by activation of idiotypic network and regulation in human body suggesting that injection of Ig into body could bring about not only passive immunity but also active immunity.

[Development of hybridomas secreting monoclonal anti-idiotypic antibodies that bear the internal image of the terminal trisaccharide of PGL-I]

Two hybridomas designated as F7B7 and F7B9 secreting monoclonal anti-idiotypic antibodies against terminal trisaccharide of PGL-I were developed by fusion of SP2/0 cells and spleen cells of BALB/c mouse immunized with mouse monoclonal anti-trisaccharide of PGL-I (MAb1-E10F1). To characterize the F7B7, the following results were obtained. First, F7B7 reacted with MAb1-E10F1 specifically. Secondly, the cross ELISA neutralizing tests gave positive results. The binding of anti-trisaccharide positive serum with trisaccharide (contained in semi-synthetic antigen, NT-O-BSA) was inhibited F7B7 and the degree of inhibition showed dose-dependent manner. The binding of anti-trisaccharide positive serum with F7B7 was inhibited by NT-O-BSA and the degree of inhibition also showed dose-dependent manner. It was concluded that the hybridoma F7B7 is able to secrete monoclonal anti-idiotypic antibodies that bear the internal image of trisaccharide of PGL-I. The potentials and advantages of monoclonal anti-idiotypic antibody F7B7 as surrogate antigen in the serodiagnosis of leprosy have been discussed.

[Monoclonal Anti-Id as substitute for HBsAg to detect Anti-HBs]

According to Jerne's idiotype-anti-idiotype network theory, a new method to detect Anti-HBs was studied. This method utilized monoclonal Anti-Id as a substitute for HBsAg of the routine method adopting the enzyme-linked immunosorbent assay (ELISA) format. The serum specimen was incubated with solid-phase (polyvinyl chloride) that had been coated with monoclonal Anti-Id. If Anti-HBs was present in the serum, it would be combined with the Anti-Id. HRP-labeled goat Anti-human IgG was added, which reacted with the immobilized Anti-HBs. Under optimal conditions, 0.5 microgram/ml Anti-HBs could be detected. This method is safe, simple, and specific for Anti-HBs with no cross-reactivity with Anti-HBs, Anti-HBe and rheumatic factor positive serum, and the reagents can be obtained in unlimited amounts and are homogeneous. These features are particularly attractive when the antigen is difficult to obtain.

Expression of two S-ribonucleases of Petunia inflata using baculovirus expression system

We have previously shown that three Petunia inflata S-proteins, products of the multiallelic S-gene of the self-incompatibility system, are ribonucleases. Here we report the expression of cDNAs for two of these S-proteins using the baculovirus expression system. S2- and S3-proteins were found in both supernatants and lysates of Spodoptera frugiperda cells infected with recombinant baculoviruses. Both recombinant S-proteins contained glycosylated (25 kD) and nonglycosylated (23 kD) forms. Recombinant S2- and S3-proteins were purified from insect cell cultures, and the amino-terminal sequences determined from glycosylated S2- and S3-proteins indicated that the leader peptide encoded by each cDNA was correctly removed. Both glycosylated and nonglycosylated forms of S2- and S3-proteins exhibited ribonuclease activity.